Sandwich panels (e.g., a core sandwiched between two layers of material, or skins) are often used in the construction of aircraft, because they have high strength-to-weight ratios. Depending on the specific location and application of a sandwich panel in an aircraft, one or more round inserts may be required to be inserted within or through a sandwich panel in order to affix one or more other structures or fasteners to the panel. Round inserts may be used to transfer localized loads (e.g., via a pin, bolt, screw, joint, or other structure) to the sandwich panel, such as to fasten the sandwich panel to another structure, join multiple sandwich panels to each other, and/or attach one or more external objects to the sandwich panel. For example, round inserts may provide a channel for wire bundles to be passed from one side of the sandwich panel to the other, or round inserts may be configured to receive a pin or bolt or other fastener in order to secure another panel or object to the sandwich panel, via the round insert. In the aerospace industry, such sandwich panels and round inserts may be used to assemble the interior main structure and/or secondary structures of the aircraft, and/or may be used to form floor boards, wall panels, galleys, stow bins, overhead compartments, lavatories, and/or other structures within the aircraft. Such sandwich panels and round inserts are also used in other industries.
FIGS. 1 and 2 illustrate a conventional round insert 10 installed in a sandwich panel 11, shown schematically in cross-section. Sandwich panel 11 may include a core 13 sandwiched between a first skin 15 and a second skin 17. First skin 15 and second skin 17 may be rigid or semi-rigid skins, and are typically relatively thin compared to core 13, which is typically formed of a lightweight material. Conventional round insert 10 may be inserted into a circular bore 19 formed in sandwich panel 11, which may be a blind bore 21 (FIG. 1) or a through-bore 23 (FIG. 2). Blind bore 21 may extend through one of the skins (e.g., first skin 15, as shown in FIG. 1) and into the core 13, towards the other skin (e.g., second skin 17), whereas through-bore 23 may extend entirely through first skin 15, second skin 17, and core 13. As shown in FIGS. 1 and 2, a flange portion 27 of conventional round insert 10 may be substantially flush with one of more of first skin 15 and second skin 17, or, as shown in FIG. 3, flange portion 27 of conventional round insert 10 may lay on top of (e.g., on an outer surface of) first skin 15 or second skin 17.
In conventional techniques, an adhesive material, such as a potting compound or epoxy, is injected through potting holes, or vents, in conventional round insert 10 to fill a gap or space 29 between conventional round insert 10 and core 13 of sandwich panel 11. The adhesive material, once fully cured, serves to secure the insert in place within circular bore 19 of sandwich panel 11, and is designed to prevent relative movement of conventional round insert 10 with respect to sandwich panel 11 and retain conventional round insert 10 within circular bore 19 (e.g., resisting pull-out, rotation, and lateral movement of conventional round insert 10) once the adhesive compound dries, solidifies, and/or cures.
However, due to variations in sizes of sandwich panels and depths of bores, dozens of different sizes of conventional inserts are needed. Often, the incorrect size insert may be installed into a given bore, due to selecting the wrong insert, and/or inaccurately determining the needed size. For example, in situations where only one side of the sandwich panel is accessible, measuring the thickness of the sandwich panel to determine the correct insert size may be difficult. Installing the wrong insert may result in significant scrap and/or rework costs. Furthermore, due to the large number of inserts that may need to be installed in a given sandwich panel or apparatus, shortages of particular sizes are common during manufacturing, due to inaccuracies. Prior art solutions have included inserts having an adjustable height, however these prior art inserts include a flange (such as flange portion 27 shown in FIG. 3) that sits on the surface of the sandwich panel, such that the insert is not flush with the panel. While these prior art inserts may address some issues in the field, they are not suitable for applications requiring a flush installation. Such issues with conventional inserts and methods of installing the same within a sandwich panel are on-going and problematic in a variety of industries.